/* Author: Ruud Harmsen, August 2021.

   Explanation:
   https://rudhar.com/sfreview/siworin/siworin14.htm
   See also:
   https://rudhar.com/sfreview/siworin/siworin15.htm

   Meant to illustrate this bug:
   https://sourceware.org/bugzilla/show_bug.cgi?id=28258
 */

#include <stdlib.h>
#include <stdio.h>
#include <locale.h>
#include <wchar.h>
#include <ctype.h>
#include <wctype.h>
#include <errno.h>

#define REPERR(LINE, ERRNO) { \
   fprintf(stderr, "Line %3d, error %d ", (LINE), (ERRNO)); \
   perror(NULL);}

char bytes[] = u8"Há, ναι, არა\n";
wchar_t chars[sizeof bytes * sizeof (wchar_t)];

int main (void)
{
   FILE *fpc, *fpw;
   int i;
   int c = 0;
   wint_t cw = 0;
   int retval;

   if (!setlocale(LC_ALL, "en_US.UTF-8"))
      REPERR(__LINE__, errno);

   for (i = 0; i < sizeof bytes && bytes[i]; i++)
   {
      retval = mbtowc(&cw, bytes + i, 8);
      fprintf(stderr, "retval = %2d, cw = \'%lc\'\n", retval,
         iswprint(cw) ? cw : L'?');

      retval = mbstowcs(chars, bytes + i, 64);
      fprintf(stderr, "retval = %2d, chars = %ls", retval, chars);
   }

   /* Write a test file to disk. */
   fpc = fopen("in", "w");
   fwrite(bytes, 1, sizeof bytes - 1, fpc);
   fclose(fpc);

   /* Open two streams for the same file, one in character mode,
      one in wide mode. */
   fpc = fopen("in", "r"); fpw = fopen("in", "r");

   fprintf(stderr, "\n");
   for (i = 0; i < sizeof bytes && bytes[i]; i++)
   {
      if ((retval = fseek(fpc, i, SEEK_SET)) < 0)
         {fprintf(stderr, "Tried to fseek to byte %d\n", i); REPERR(__LINE__, errno);}

      if ((retval = fseek(fpw, i, SEEK_SET)) < 0)
         {fprintf(stderr, "Tried to fseek to byte %d\n", i); REPERR(__LINE__, errno);}

      c = fgetc(fpc);
      if (ferror(fpc)) {REPERR(__LINE__, errno); clearerr(fpc);}
      cw = fgetwc(fpw);
      if (ferror(fpw)) {REPERR(__LINE__, errno); clearerr(fpw);}

      if (feof(fpc) || feof(fpw))
         break;

      fprintf(stderr, "Pos %2d, char %02x-%c, wide char %08x-%lc\n",
         i, c , isprint (c)  ? c  :  '?',
            cw, iswprint(cw) ? cw : L'?');
   }
   fclose(fpc); fclose(fpw);

   return 0;
}